A semiconductor memory device is provided. A semiconductor memory is a memory device embodied by using a semiconductor such as silicon Si, germanium Ge, gallium arsenide GaAs, indium phospide Inp, etc. Typically, a semiconductor memory device may be either a volatile memory device or a non-volatile memory device.
A volatile memory device is a memory device where stored data becomes lost if power is not supplied. Examples of volatile memory devices include a static RAM (SRAM), a dynamic RAM (DRAM), a synchronous DRAM (SDRAM) and so on. A non-volatile memory device is a memory device where stored data remains even when a power is not supplied. Examples of non-volatile memory devices include read only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable and programmable ROM (EEPROM), flash memory, phase-change RAM (PRAM), magnetic RAM (MRAM), resistive RAM (RRAM), ferroelectric RAM (FRAM), etc. Flash memory, which may be the most common and well-known non-volatile memory device, includes a NOR-type memory device and a NAND-type memory device.
Semiconductor memory devices having three-dimensional array structure have been studied to enhance integrity of the semiconductor memory device. In order to produce such devices, it is important to secure reliability of a program operation, a read operation and an erase operation.